There exists a variety of designs for tubing administration sets for delivering medical liquids or solutions to patients. These administration sets vary widely in their particular uses and designs. Drip chambers often are included, in-line, in fluid administration sets. Principal functions of the drip chambers, among others, are to assist in priming the administration set in order to commence the flow of liquid to the patient and to permit medical personnel to determine the flow rate of the fluid through the administration set by counting the number of falling drops in a given period of time.
Electronic drop counting devices have been designed to be used in conjunction with administration sets and drip chambers for situations where long term monitoring of solution infusion rate is necessary or desirable. Drop counting devices typically function by using a light source and a photoreceptor having associated electronic circuitry. Drops of fluid entering the drip chamber will interrupt the light beam directed to the photoreceptor causing changes in the electronic circuitry. Individual drops of liquid may be counted in this manner. Flow rates can be calculated by electronically monitoring the number of drops in a given period of time and using known drop volumes for particular fluids.
Conventionally available fluid administration sets are sold having drip chambers of various shapes and sizes, but all of the drip chambers can suffer from a significant shortcoming which can result in erroneous fluid flow rate calculation. Erroneous flow rate readings predominently are caused by fluid splash back or fluid bounce back.
More precisely, in conventional drip chambers, a certain volume of fluid resides in the bottom portion of the drip chamber. Fluid exiting the drip chamber typically is replaced at a rate greater than or equal to the rate of fluid entering the drip chamber. Fluid droplets striking the surface of this retained fluid can be reflected back upward in the direction of their fall, namely, the principal droplets entering the chamber appear to be reflected back upward. Not wishing to be limited to any theory of operation, it appears that the mechanism of splash back is rather like a falling body bouncing on a trampoline. Principal droplets should be distinguished from dispersed droplets caused by the impact of the entering principal droplets. Principal drops or droplets are defined as fluid drops entering the drip chamber after being formed in a drop former. This fluid splash back or bounce back can result in erroneous flow rate readings. Often, these upwardly redirected principal fluid droplets again will be detected by the electronic drop counter and register as another drop of fluid entering the drip chamber. It is believed that the surface tension or surface energy characteristics of both the fluid and the interior surfaces of the drip chamber effect this fluid splash back or bounce back.
It would be advantageous to reduce or substantially eliminate splash back or bounce back in a drip chamber thereby avoiding erroneous indications of fluid flow.
It would be expedient to provide a drip chamber having surface tension or surface energy characteristics such that the phenomenon of droplet splash back or bounce back was eliminated.
Also, it would be expedient to have an administration set for use with a drop counter whereby erroneous indication of fluid flow by a drop counter would be eliminated or greatly reduced as a source of error.